1. Technical Field
Embodiments described herein relate to a hybrid drive system for a vehicle having an internal combustion engine (engine) and an electric motor generator (motor generator) as a drive source for driving.
2. Related Art
As this type of drive system for a vehicle in the related art, as disclosed in JP-T-2005-502543, a hybrid drive system for a vehicle in which an engine, a transmission, and a motor generator are combined is known. FIG. 13 is an outline diagram illustrating the drive system disclosed in JP-T-2005-502543, and FIG. 14 is a block diagram schematically illustrating a configuration thereof.
As illustrated in FIGS. 13 and 14, in this drive system, an input shaft of a transmission TM is connected to an output shaft of an engine ENG, and a differential case of a differential device DIFF leading to drive wheels 2 is connected to an output shaft of the transmission TM through a one-way clutch OWC. The one-way clutch OWC is incorporated into the transmission mechanism as an element thereof because the transmission mechanism TM is configured by an eccentric drive device. In addition, the motor generator MG is connected to the input shaft (output shaft of the engine ENG) of the transmission TM through a first clutch CL1 and is connected to the differential case of the differential device DIFF through a second clutch CL2 and a gear set GEAR.
In this drive system, engine driving only using the driving force of the engine ENG, EV driving only using the driving force of the motor generator MG, and parallel driving using both of the driving force of the engine ENG and the driving force of the motor generator MG can be performed. In addition, by using the regenerative operation of the motor generator MG, regenerative energy can be obtained during deceleration and regenerative braking can work for the drive wheels 2 at the same time. In addition, the motor generator MG can start the engine ENG
However, similar to the above-described drive system, in the case of a system having the one-way clutch OWC on a power transmission pathway which transmits the rotational power of the engine ENG to the drive wheel 2 side, when the rotating speed on the downstream side of the one-way clutch OWC is higher than that on the upstream side thereof, the one-way clutch OWC blocks the power transmission. As a result, the power is not transmitted from the drive wheel 2 side to the engine ENG side. Therefore, when the rotating speed on the downstream side of the one-way clutch OWC becomes higher than that on the upstream side by, for example, releasing (disengaging) an accelerator pedal, the first clutch CL1 is disengaged and the second clutch CL2 is engaged. Accordingly, driving in which the motor generator MG regenerates the power on the drive wheel 2 side and regenerative braking works for the drive wheel 2 side at the same time can be selected.
In addition, during this time, in a range not causing the one-way clutch OWC to be in a connected state, the engine ENG can be maintained in an idle state or in an idle stop state. In the case where the engine ENG is maintained in the idle state, when the drive system is switched to engine driving thereafter, the rotating speed of the engine can be increased up to a required rotating speed immediately. Therefore, the response can be improved. In addition, in the case where the engine is set to the idle stop state, fuel consumption can be suppressed correspondingly. When the engine starts in the idle stop state, it is necessary that the motor generator MG crank the engine ENG by engaging the first clutch CL1 and disengaging the second clutch CL2.
As described above, when the engine ENG waits in the idle state, the drive system can be switched to engine driving with a good response, but there is a problem with fuel consumption for idling. On the other hand, when the engine ENG waits in the idle stop state, fuel consumption can be suppressed as compared to the case of waiting in the idle state, but it is necessary that the motor generator MG start the engine ENG by engaging the first clutch CL1 and disengaging the second clutch CL2 and that the rotating speed of the engine be increased up to a rotating speed capable of transmitting torque. During that time, unnecessary time is taken and thus there is a problem that the above operation cannot be performed with a good response.